FIG. 9 is a perspective view of a protrusion, on housing 300 of a prior art switching roller finger follower, for engaging ends stops on a secondary arm.
FIG. 10 is a perspective view of end stops on prior art secondary arm 302. The following should be viewed in light of FIGS. 9 and 10. Transport and overswing ends stops are used in switching roller finger followers to prevent excessive rotation of secondary arms, which can cause damage to the follower, as a result of malfunction of the follower.
For example, as is known in the art, a locking pin (not shown) is used to block rotation of the secondary arms during a locked mode. For example, end 304 of arm 302 is arranged to contact the locking pin when force from a cam lobe (not shown) engaged with surface 306 of arm 302 causes arm 302 to rotate in direction RTD1. If the locking pin does not displace the proper distance at the proper time (a mis-switch), the force from the cam lobe causes end 304 to slide past the locking pin so that arm 302 continues to rotate in direction RTD1. Overswing endstop 308, formed in arm 302, is configured to engage protrusion 310 on housing 300 to block further rotation in direction RTD1. However, a large rotational force is imparted to arm 302 by the cam lobe and the magnitude of this force can cause endstop 308 to shear protrusion 310 from housing 300 causing further rotation of arm 302. This further rotation can cause failure of a follower including housing 300 and arm 302. For example, a lost motion spring (not shown) engaged with arm 302 is used to urge arm 302 in direction RTD2, opposite RTD1, as described below. If arm 302 is rotated too far in direction RTD1, the spring is overstressed, resulting in various failure modes for a switching roller finger follower including housing 300 and arm 302.
After a mis-switch in the locked mode, the locking pin retracts to enable rotation of the secondary arm in direction RTD2 via a spring (not shown). Rotation of the secondary arm in direction RTD2 is blocked by contact of transport endstop 312, formed in secondary arm 302, with protrusion 310. The rotation of the secondary arm in direction RTD1 is opposed by the spring force of the spring. The additional rotation of the secondary arm due to the mis-switch results in an increase in the spring force, which further results in an increase of the force applied by endstop 312 to protrusion 310. The magnitude of this force can cause endstop 308 to shear protrusion 310 from housing 300 enabling excess rotation of arm 302 in direction RTD2, which can cause failure of a follower including housing 300 and arm 302.